Changing elements in an array

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Elizabeth
Elizabeth 2014-4-19
评论： Image Analyst 2014-4-19
I have an array of L zeros. I'm working on a program that changes the state of the elements (ones to zeros and zeros to ones). The first time through I change every element. The second time through every second element. The third time through every third element and so on to the Lth time.
I'm thinking some type of loop, similar to a Josephus problem. Somehow counting to every nth element, comparing it, and changing it. But I'm not sure of how to change to looking at the next nths (the previous n plus 1) to Lth element each loop.

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回答（1 个）

Image Analyst
Image Analyst 2014-4-19
Do you mean like this:
clc;
vec = randi(2, 1, 30) - 1; % Random array of 1's and zeros.
L = sum(vec==0)
for k = 1 : L-1
selector = 1 : k : length(vec)
vec(selector) = ~vec(selector)
end
  2 个评论
Elizabeth
Elizabeth 2014-4-19
This does not start with a zero vector and changes the first element and counts off from there. So when selecting every 3rd element it selects the first then fourth instead of the third then sixth.
Image Analyst
Image Analyst 2014-4-19
So change it to start with zero. No big deal. I assumed that you would already have vec so I just made up something. Don't use mine - use yours.
For the n'th element if you want to start it at element #n, then do so.
selector = n : n : length(vec); % Basic MATLAB concept....

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